Transcript Respiratory System

Respiratory System
Factoids
• Your lungs contain almost 1500 miles of
airways and over 300 million alveoli.
• Every minute you breathe in 13 pints of air.
Primary function
• obtain oxygen for use by body's cells &
eliminate carbon dioxide that cells produce
Respiratory system includes:
• airways leading into (& out of) lungs plus
the lungs themselves
• Pathway of air: nasal cavities (or oral
cavity) > pharynx > trachea > primary
bronchi (right & left) > secondary bronchi >
tertiary bronchi > bronchioles > alveoli
(site of gas exchange)
• The exchange of gases (O2 & CO2)
between the alveoli & the blood occurs by
simple diffusion
Breathing is an active process
• - requiring the contraction of skeletal
muscles. The primary muscles of
respiration include:
– the external intercostal muscles (located
between the ribs)
– and the diaphragm (a sheet of muscle located
between the thoracic & abdominal cavities).
• During inhalation
• -the diaphragm contracts (becomes less
dome shaped)
• -the rib muscles contract
• -the rib cage moves up and out.
These movements, enlarge the volume of
the thoracic cavity, causing the pressure in
the lungs to become lower than air
pressure, and air will move into the lungs.
b. During exhalation
• -diaphragm relaxes (becomes more
domed shaped)
• -the rib muscles relax
• -the rib cage moves down and in
• These movements decrease the volume of
the thoracic cavity, causing the pressure in
the lungs to become greater than air
pressure and air is forced out of the lungs.
• The walls of alveoli are coated with a thin
film of water & this creates a potential
problem.
• Water molecules are attracted to each
other - surface tension.
• This surface tension increases as water
molecules come closer together, which is
what happens when we exhale & our
alveoli become smaller (like air leaving a
balloon).
• Potentially, surface tension could cause
alveoli to collapse. If alveoli collapsed
they'd contain no air & no oxygen to
diffuse into the blood.
• To solve problem, the lungs produce a
substance called surfactant that reduces
surface tension.
How the Structure of the Alveoli
is Related to its Function
a. Each
alveolus is thin (0.1 to 0.2 mm in diameter). Allows
for faster exchange of gases.
b. The walls of the capillaries and the alveoli are each
made up of a single layer of cells – short distance so
gases can be exchanged quickly
c. A film of surfactant (a lipoprotein) covers the alveoli. This
lowers surface tension and prevents the alveoli from
collapsing.
d. There is a lot of blood supplied to the alveoli via
capillaries. This allows for faster exchange of gases
e. There are approximately 150 million alveoli. The large
number increases surface area.
How are oxygen & carbon
dioxide transported in the
blood?
• Oxygen is carried in blood:
• 1 - bound to hemoglobin (98.5% of all
oxygen in the blood)
• 2 - dissolved in the plasma (1.5%)
Carbon dioxide
• - transported from the body cells back to
the lungs as:
• 1 - bicarbonate (HCO3) - 60%
• 2 - carbaminohemoglobin - 30%
– formed when CO2 combines with hemoglobin
(hemoglobin molecules that have given up
their oxygen)
• 3 - dissolved in the plasma - 10%
• Control of Respiration
• Your respiratory rate changes. When
active, for example, your respiratory rate
goes up; when less active, or sleeping, the
rate goes down. Also, even though the
respiratory muscles are voluntary, you
can't consciously control them when you're
sleeping.
• Function of the Pleural Membranes
- A thin membrane called the pleura
surrounds each lung and lines the thoracic
cavity.
- The pleura secretes a small amount of
fluid that lubricates each surface, so that
they slide past one another as the lungs
expand and contract
• Function of cilia in the respiratory tract
-beat continuously , pushing mucus and
foreign particles embedded in mucus up
towards the pharynx where it is swallowed
Tobacco
paralyzes cilia
– they cannot
sweep debris
out of air
passages.
• Cigarette smoke prevents the cilia from beating
and stimulates mucus secretion.
• Coughing is necessary to expel excess mucous
but it contributes to bronchitis and emphysema.
• Cigarette smoke also kills phagocytic cells in
respiratory epithelium. These cells normally help
rid the lungs of foreign particles and bacteria.
• Cigarette smoke contains compounds that are
modified in the body to form carcinogens.
• Smoking causes 80% of lung cancer deaths.
Cancerous lung